Linear Adsorption Enables NO Selective Electroreduction to Hydroxylamine on Single Co Sites

Hydroxylamine (NH₂ OH), a vital industrial feedstock, is presently synthesized under harsh conditions with serious environmental and energy concerns. Electrocatalytic nitric oxide (NO) reduction is attractive for the production of hydroxylamine under ambient conditions. However, hydroxylamine selectivity is limited by the competitive reaction of ammonia production. Herein, we regulate the adsorption configuration of NO by adjusting the atomic structure of catalysts to control the product selectivity. Co single-atom catalysts show state-of-the-art NH₂ OH selectivity from NO electroreduction under neutral conditions (FE NH 2 OH ${{_{{\rm NH}{_{2}}{\rm OH}}}}$ : 81.3 %), while Co nanoparticles are inclined to generate ammonia (FE NH 3 ${{_{{\rm NH}{_{3}}}}}$ : 92.3 %). A series of in situ characterizations and theoretical simulations unveil that linear adsorption of NO on isolated Co sites enables hydroxylamine formation and bridge adsorption of NO on adjacent Co sites induces the production of ammonia.